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In integrated semiconductor technology and the chemical trace analysis used therefor, chemicals are required which are frequently not commercially available with the high purity desired.
English (United States)
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Method of Producing Highly Pure Chemicals
In integrated semiconductor technology and the chemical trace analysis
used therefor, chemicals are required which are frequently not commercially
available with the high purity desired.
The chemicals ranging from deionized water to, for example, concentrated
nitric acid contain about 10/-15/ to 10/-10/ % metallic impurities.
The method described below permits the removal from such chemicals of a
large part of the residual metallic impurities. The chemical to be purified is
introduced in a frozen or crystalline state into a suitably tempered ultracentrifuge.
As a function of the duration of centrifugation and the centrifugal force, the
impurities migrate preferably in a radial direction, accumulating in the outer or
inner area of the solid chemical. By melting off or chemically or mechanically
removing the inner or outer area, a highly pure chemical is obtained.
This method permits a ready purification even of aggressive chemical
compounds, since the change of the compound to the solid state can take place
outside the centrifuge.